In recent years, a toner for developing an electrostatic image (hereafter, it is called simply as “a toner”) of an image forming apparatus using an electrophotographic method is required to be thermally fixed at a lower temperature in order to achieve high print speed and further energy saving for the purpose of decrease of load to the environment. Such toner is required to have a binder resin of a low melting point or a low viscosity. It was proposed a toner enabling to improve low-temperature fixability by adding a crystalline resin such as a crystalline polyester resin as a plasticizer (fixing auxiliary agent).
For example, in Patent document 1 (JP-A No. 2008-090054), it was proposed a technology which makes possible to achieve excellent cleaning property, and a good balance between low-temperature fixability and thermal resistance by defining an acid value of each color toner containing a crystalline polyester resin in a color toner set having a plurality of colors.
Further, Patent document 2 (JP-A No. 2014-35506) disclosed a technology to achieve excellent charge stability, as well as a good balance between low-temperature fixability and thermal resistance by using a specific alkyl (meth)acrylate monomer in a toner containing a crystalline polyester compound and a styrene-acrylic resin.
However, it is important for a toner not only to achieve a good balance between low-temperature fixability and thermal resistance, but also to be provided with excellent document offset property (image storage property), color gamut (color reproducibility), and further, environmental charge stability that will not exhibit difference of charge depending on the environment. It is required a toner having all of these properties.